class Car:  
    def __init__(self, make, model, year, odometer=0):  
        self.make = make  
        self.model = model  
        self.year = year  
        self.odometer = odometer  
  
    def get_descriptive_name(self):  
        return f"{self.year} {self.make} {self.model}"  
  
    def get_odometer(self):  
        print(f"This car has {self.odometer} miles on it.")  
  
    def update_odometer(self, new_odometer):  
        if new_odometer >= self.odometer:  
            self.odometer = new_odometer  
        else:  
            print("You can't roll back odometer!")  
  

my_car = Car("Toyota", "Rav4", 2021)  

print(my_car.get_descriptive_name())  
  
my_car.get_odometer()  
  
my_car.update_odometer(23)  
  
my_car.get_odometer()  